Practical GuideForensics

Digital Forensics & Investigation Guide

Comprehensive methodology for conducting digital forensics investigations in telecommunications networks, from evidence collection to legal proceedings.

Overview

Digital forensics in telecommunications requires specialized knowledge of signaling protocols, network architecture, and legal requirements. This guide provides a comprehensive framework for investigating security incidents, collecting evidence, and supporting legal proceedings.

Critical: Improper evidence handling can render findings inadmissible in court. Always follow chain of custody procedures and consult legal counsel before beginning investigations.

Investigation Phases

24-72h

Critical Evidence Window

100%

Chain of Custody Required

Investigation Methodology

7-phase forensic investigation process

Phase 1: Preparation

• Establish forensic readiness program

• Deploy logging and monitoring infrastructure

• Create forensic toolkit and procedures

• Train investigation team

• Establish legal and compliance framework

• Document network architecture and data flows

Phase 2: Identification

• Detect and confirm security incident

• Determine scope and impact

• Identify affected systems and data

• Assess legal and regulatory requirements

• Notify stakeholders and authorities

• Assemble investigation team

Phase 3: Preservation

• Isolate affected systems (if appropriate)

• Prevent evidence tampering or destruction

• Create forensic images of storage media

• Capture volatile memory (RAM dumps)

• Preserve network traffic captures

• Document chain of custody

Phase 4: Collection

• Collect logs from all relevant systems

• Extract signaling protocol data (SS7, Diameter, SIP)

• Gather network flow data and packet captures

• Collect authentication and access logs

• Obtain configuration files and change records

• Document collection methodology

Phase 5: Analysis

• Timeline reconstruction of events

• Correlation of data from multiple sources

• Identification of attack vectors and techniques

• Attribution analysis (if possible)

• Impact assessment and data exfiltration analysis

• Root cause determination

Phase 6: Documentation

• Create detailed investigation report

• Document findings with supporting evidence

• Maintain complete chain of custody records

• Prepare executive summary for leadership

• Create technical appendices

• Ensure legal admissibility of documentation

Phase 7: Presentation

• Present findings to stakeholders

• Provide expert testimony (if required)

• Support legal proceedings

• Communicate with regulators

• Share lessons learned internally

• Update security controls based on findings

Evidence Collection

Telecommunications-specific evidence sources

Network Infrastructure Evidence

Signaling System Logs: SS7, Diameter, SIP message logs with timestamps, source/destination addresses, and message content

Network Element Logs: HLR/HSS, MSC, SGSN/GGSN, MME, SGW/PGW authentication and session logs

Firewall & IDS/IPS Logs: Network traffic patterns, blocked connections, intrusion attempts

CDR/xDR Records: Call Detail Records, Charging Data Records for billing and usage analysis

PCAP Files: Full packet captures from strategic network points

System & Application Evidence

Authentication Logs: RADIUS, TACACS+, LDAP/AD authentication attempts and failures

Database Audit Logs: Subscriber database queries, modifications, and access patterns

Application Logs: BSS/OSS system logs, customer care system access logs

Configuration Files: Network element configurations, change management records

Memory Dumps: RAM captures from compromised systems for malware analysis

Mobile Device Evidence

SIM Card Data: IMSI, Ki, authentication records, SMS storage

Device Logs: Call logs, SMS/MMS records, application data, location history

Network Registration: Cell tower connection history, handover records

Application Data: Messaging apps, social media, browser history

Forensic Tools & Techniques

Essential tools for telecommunications forensics

Network Forensics

• Wireshark - Packet analysis

• tcpdump - Packet capture

• NetworkMiner - Network forensic analysis

• Zeek (Bro) - Network security monitoring

• Moloch - Large-scale packet capture

Signaling Analysis

• SS7 Protocol Analyzers

• Diameter Protocol Decoders

• SIP Traffic Analyzers

• GTP Tunnel Inspection Tools

• Custom Protocol Parsers

Disk & Memory Forensics

• FTK Imager - Disk imaging

• Autopsy - Digital forensics platform

• Volatility - Memory forensics

• Sleuth Kit - File system analysis

• EnCase - Enterprise forensics

Mobile Forensics

• Cellebrite UFED - Mobile extraction

• Oxygen Forensics - Mobile analysis

• Magnet AXIOM - Digital evidence

• SIM Card Readers

• IMSI Catcher Detectors

Log Analysis

• Splunk - Log aggregation & analysis

• ELK Stack - Log management

• Graylog - Log analysis platform

• LogRhythm - SIEM with forensics

• Custom Log Parsers

Malware Analysis

• IDA Pro - Disassembler

• Ghidra - Reverse engineering

• Cuckoo Sandbox - Malware analysis

• YARA - Malware identification

• VirusTotal - Malware scanning

Legal Considerations

Legal and regulatory requirements for forensic investigations

Legal Disclaimer: This guide provides general information only. Always consult with legal counsel before conducting forensic investigations, especially those involving law enforcement or legal proceedings.

Chain of Custody

Documentation: Record who collected evidence, when, where, and how it was handled

Integrity: Use cryptographic hashes (SHA-256) to verify evidence hasn't been altered

Storage: Secure evidence in tamper-evident containers with restricted access

Transfer: Document every transfer of evidence between parties

Privacy & Data Protection

GDPR Compliance: Ensure lawful basis for processing personal data during investigations

Data Minimization: Collect only data necessary for the investigation

Retention Limits: Define and enforce evidence retention periods

Access Controls: Limit evidence access to authorized investigators only

Regulatory Requirements

Breach Notification: Comply with 72-hour GDPR notification requirements

Law Enforcement Cooperation: Understand legal obligations for cooperating with authorities

Industry Standards: Follow ISO 27037, NIST SP 800-86 forensic guidelines

Expert Testimony: Maintain professional certifications (GCFA, EnCE, CCFP)

Investigation Report Template

Standard structure for forensic investigation reports

1. Executive Summary

High-level overview of incident, findings, and recommendations for non-technical stakeholders

2. Incident Overview

Timeline, affected systems, initial detection, scope and impact assessment

3. Investigation Methodology

Tools used, evidence sources, analysis techniques, limitations and constraints

4. Evidence Analysis

Detailed findings from each evidence source, timeline reconstruction, attack vector analysis

5. Root Cause Analysis

How the incident occurred, vulnerabilities exploited, contributing factors

6. Impact Assessment

Data compromised, systems affected, business impact, regulatory implications

7. Recommendations

Immediate actions, short-term improvements, long-term strategic changes

8. Appendices

Chain of custody records, technical evidence details, tool outputs, supporting documentation

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